Project Summary While many neurological defects and disorders are known to result from developmental perturbations in specific cell types and/or are linked to well-studied signaling pathways, the system-level coordination of multiple cell populations and the spatiotemporal specificity of their signaling outputs during neurogenesis remains poorly understood. The long-term objective of this proposal is to take advantage of the accessible and rapidly developing zebrafish olfactory epithelium to quantitatively characterize cell-cell signaling pathways and multicellular behaviors that drive the assembly of complex neuronal populations in vertebrates. Proposed experiments will test the hypothesis that the Notch and Wnt signaling pathways provide spatially- and temporally- sensitive cues to guide stem cell migration into the olfactory epithelium and regulate sensory neurogenesis. Small subsets of cells will be manipulated and analyzed completely in vivo, at subcellular spatial resolution and with sub-minute temporal resolution, so as to determine the system-level coordination of stem cell migration, specification, and differentiation during both normal and disrupted signaling. First, new tools and techniques will be used to perturb Wnt signaling in vivo at specific times and locations during olfactory development and to algorithmically model and explain progenitor cells? migratory behavior. Next, Notch signaling will be manipulated in vivo to quantitate its effects on olfactory system-wide neurogenesis, and target genes will be identified that are required for neuronal specification and/or differentiation. Finally, the transcription factor insm1a will be similarly investigated to determine its role in Notch signaling-mediated olfactory neurogenesis. The approaches in this proposal will directly analyze in vivo data to understand and predict multicellular behavior without reducing biological complexity and help uncover phenotypes that may advance our broad understanding of system-wide neuronal differentiation and assembly in vivo.